A small placement change made during routing because the router proved a region could not be routed. Traditional term.
How it looks
Drawing: illustration of the idea, not a CORE3588 route
Illustration: a gap between two parts that has room for two tracks while three nets must pass through it. No amount of clever routing fixes this; only moving a part does.
How it works
Where it fits
A small correction to placement; the bigger version is choosing a different floorplan.
In Ants it is one of the moves of the co-design loop, so it needs Nidhish's yes.